The present invention relates to shampoo compositions, and more particularly to shampoo compositions containing non-volatile silicone materials which condition the hair leaving it softer and more manageable.
When washing the hair with conventional shampoo compositions, the natural oils are removed together with the dirt and unwanted oils. When too much of the natural oil is removed, for example by especially frequent washing, the hair becomes less easy to comb or style, and subject to static build-up causing "flyaway".
Hair conditioners have been developed to try to restore the condition of the hair. These compositions are normally applied to the hair after shampooing, left on the hair for a period of time and rinsed off. This process is time consuming and expensive since two separate products are needed.
Conditioning shampoos containing cationic conditioning agents have been disclosed for example in EP 18 717 (Unilever). These cationic agents confer some conditioning benefit on the hair, but are often thought to leave a residue on the hair, which may cause dulling on dry hair.
Silicone oils are known to be conditioning agents and their use in conditioning shampoos has been proposed for example in EP 74 264 (Unilever) and EP 77 920 (Kao). However, it has been found that care is needed when formulating silicone containing shampoos as the compositions are often unstable and the silicone oil tends to separate out.
Conventional pearliser materials such as ethylene glycol stearates have been used to suspend silicone materials (EP 181 773, Procter & Gamble). These pearlisers are formed by cooling an aqueous emulsion of liquid ethylene glycol mono- and/or di-stearate, giving rise to a range of waxy crystal leaflets or needles having a range of different sizes and crystal habits. It is difficult to obtain a narrow size distribution, and even when concentrated pearliser pastes are obtained commercially, control of the crystal habit is not assured. Pearliser crystals have been found to separate when incorporated in shampoos with the dual function of pearlising the composition and suspending other materials.
Titanium dioxide coated mica particles on the other hand are free of this problem of instability, in part because the process of manufacture may be regulated to ensure a tighter size distribution, and also because the dry particles may easily be sieved.